In industrial plants, valves are repaired frequently. Valves which are welded into the pipe are usually repaired in place due to the expense related to removal and reinstallation. Linear acting valves of the gate and globe style have a bonnet, which when removed, gives access to the internal parts of the valve. Valves which have flanged or clamped pipe connections can be either repaired in place or removed to a shop for repair. Shop repair is preferred, when feasible, due to the ability to shop test valves after the seat and sealing members have been restored. Also, a shop is a more ideal working environment compared to an insitu job and repair quality is generally better.
A problem arises with split body or side entry ball and butterfly (rotary) valves when repairs are necessary and the valves are welded in line, or flanged (or clamped) but not feasible to remove due to space restrictions, or a limited available repair time. Valves of this type do not have a bonnet which can be removed to access the valve internals.
If a split body valve is welded into the line, the line must be cut so that the body bolts can be removed to access the internal valve member. Cutting a pipeline is very costly. After lines greater than 21/2" are cut the pipe ends and the valve ends have to be machined to achieve the beveled butt weld end dimension in accordance with American National Standard Institute B16.25. Then after the valve has been repaired it must be rewelded back into the flowline. Finally, depending on the nature of the valve installation, non-destructive testing, ranging from dye checking to full penetration x-ray is done. Removal and reinstallation costs often are the most expensive step in the repair of a welded in split body or end entry valve.
Some manufacturers of split body valves will suggest removing the body bolts and pulling the valve apart. The problems with this method are many. The piping to which the valve is attached, cannot be sprung apart without placing undesirable stresses in the piping. These stresses can become the root cause of future pipe rupture, which can be catastrophic in high pressure or hazardous medium situations. Furthermore, even after using the heavy duty slings and come-alongs to spread the valve apart, there is usually not enough space between the two sections of the split body to properly remove and reinstall the internals, and, misaligned trim (internals) is often the result. Lastly, but not least, this method can also be very dangerous as there is a risk of the sprung pipe letting go or moving. If this were to happen while repair personnel were working in the valve, that part of the mechanic's body (head, hands, arms, etc.) which is between the two valve body sections could be crushed.
Two of the three primary types of industrial service rotary valves have inline repairable (bonneted) designs. They are top entry (spherical plug) ball valves and plug (tapered and straight cylinder) valves. The other rotary valve widely used in the industrial/commercial environment is the butterfly valve. Butterfly valves are made in a side entry design, and therefore are not inline repairable. To repair a butterfly valve at least one valve pipe connection must be opened. It suffers from the same problems that a split body or side entry ball valve does when it comes to insitu repair. Tapered plug valves, due to their requirement to have linear seating force (gravity and/or often some mechanical assist) are generally always top or bottom entry. While the technology described in this patent is presently indicative of that found in the spherical, near spherical or partially spherical plug (ball) and the butterfly valve, it is not intended to exclude its application to plug valve art.
Several types of top entry, inline repairable ball valves have been proposed--for example, in the U.S. Pat. Nos. 2,998,223 to Baxter (1961), 4,562,860 to Walter, Costa, and Eminger (1986), 4,637,421 to Stunkard (1986), 4,718,444 to Boelte (1988), 3,154,094 and 3,179,121 to Bredtschneider et al. (1961). All of these patents were issued for resilient seated valves with a service limitation of about 450 degrees Fahrenheit. Resilient seats, often made of Teflon brand PTFE (polymer) a trademark of E.I. duPont de Nemours & Company, Wilmington, Del., USA, can be forced into a confined ball and seat ring(s) cavity from the top down as is done in a top entry ball valve. It is important to note that this forcing of the valve trim often results in damaged balls and soft seat rings rendering the valve useless as a positive isolation device. Changing the soft seats out of a top entry ball valve is likened to changing a bicycle tire. There is a lot of prying and pinching and often the resilient seat material, like the tire inner tube, gets punctured. The difference between the tire and the valve seals is that a tire can be patched while the valve seals, once damaged by a screwdriver or any other prying instrument, are scrap. For this reason, the easy assembly of the split and side entry body is widely used. A means by which resilient seats could be installed, while the valve is completely connected to the pipe, and at the same time minimizing the risk of damaging them in the process, would advance the art.
The problems found with installing valve components in a top entry soft seated valve are compounded in a metal seated valve, as there is much less compressibility in the metal internals as they are forced into the valve, compared to the soft, low friction surface of resilient seat material. Ironically, it is with metal seated valves that some type of valve internal access is vital to the long term user acceptance as valves of this type are, due to severe service conditions, more inclined to be welded in place, especially in power plant environments.
Many high temperature ball valves are of the floating ball design. With this design the ball is suspended between a belleville spring loaded upstream guide and the downstream valve seat. Both the upstream guide and the valve seat are radiused to mate with the spherical shape of the ball. The spring is essential to the accommodation of thermally induced movement of the valve components which occurs in high temperatures services. The spring loads are best applied by a compression of the seat/ball/upstream guide and belleville spring along the flow axis of the valve. Use of the split body or side entry enables a loading force to be applied against the guide spring as torque is being applied to the fasteners that join the valve body parts together.
(a) U.S. Pat. No. 5,313,976 to Beasley (1994) discloses a top entry floating ball design valve. Using a smooth planar wall surface and a special square belleville, this design is an attempt to solve the problem of assembling a valve with a spring loaded guides from the top down. With this design the downward force (perpendicular to the flowline axis) needed to urge the square spring into the narrow gap between the body wall and the upstream ball guide can compromise alignment by cocking the guide and ball components. Also, this design may work at the first factory assembly, however, once a valve has been in service the smoother planar wall will no longer be smooth and will require restoration to render it useful each time the valve is repaired. Field machining the planar wall will be very difficult because special tooling may be required to true up the bottom corners of the square area.
(b) Furthermore, planar wall restoration will result in the need for thicker (oversized) belleville spring to make up for the material lost to a grinding and/or machining operation. This problem becomes especially apparent when the ball and seat required a substantial surface repair in way of machining, grinding and lapping, further reducing the compression value of the guide spring. It then becomes a maintenance problem having to order a special spring when the valve is repaired, especially since the size of the spring may not be known until the smoothing out of the planar wall (and member seat) is finished. By this time it may be too late to purchase a specialized spring due to factory lead times. Reusing the old belleville with a diminished critical ball loading dimension can result in valve seat failure, and, a lock-up condition wherein the ball drops and becomes seized and inoperable.
(c) Lastly, in regards to the Beasley design, in an attempt to make the insertion of the square belleville easier its strength can be compromised due to size reduction. This can result in premature spring failure and the same problems as with undersized springs as indicated above.
Now that ball valves are being used as flow control valves in high pressure and temperature service it is important to have a valve body design that permits nondestructive access to the internal members. Control valves, especially those involved with severe pressure breakdown in the order of thousands of pounds per square inch, experience accelerated wear. Therefore inspection and repair are done frequently.
(d) U.S. Pat. No. 5,305,986 to Hunt (1994) discloses a split body (floating) ball valve which due to its high temperature and pressure capability, is very likely to be welded into the pipeline. Being a split body valve presents a major drawback to this design since every time the valve is in need of inspection and repair the line must be cut and rewelded. Being able to effectively spring load the guide and yet have easy access to the inner workings of this valve would be a significant improvement of this design.
(e) With respect to non-rotary valve prior art, there are hundreds of patents which disclose various designs of gate and globe valves for use in industrial plant services. In high pressure and temperature applications, such as those existing in power plants, the gate and globe valve seats are permanently attached to the valve body. Therefore, seat grinding, machining and very often, minor and major weld repairs, must take place at the valve location, as most power plant feed water and steam valves are welded in the line. Not being able to remove the valve to a shop means that specialized portable tools must be brought to the site. This tooling, besides being expensive to make, purchase, or difficult to schedule when rented (with or without an engineer/technician), is often very difficult to setup, and, does not usually bring the same surface finish results as does a machine shape with heavier, stationary lathes, boring mills, etc. Undesirable machine tool surface chattering is a field problem encountered when using lighter weight portable machines to cut very hard metallic valve seats.
(f) Furthermore, there are many industrial repair situations where it is unsafe to expose workers to the area immediately surrounding a valve. Nuclear plant valves are a good example of this. When extensive valve seat repairs are necessary it is not unusual to use up several technicians' radiation exposure allowances. Hazardous chemical environments are another example of this.
(g) Also, as is often the case with smaller (3 inch and under) high pressure (ANSI Class 1500, 2500 and 4500) gate and globe valves, once the valve seat is damaged and repaired to a point where the seating material is gone, the valve, which is in otherwise good condition is cut out of the line and discarded.
(h) Flanged end joints are often the preferred design for valves where, due to a split body, end entry (rotary valves) or low pressure service (gate and globe valves) the valves are removed from the pipe for maintenance. Collectively, flanged end valves present a serious environmental problem due to the known leak rate of this connection method. The Clean Air Act is guiding industrial plants to ways to reduce harmful fugitive emissions.
(i) In addition to concerns about fugitive emissions and worker safety in the chemical industry, many industrial plants would prefer to weld valves in line, rather than flange them, if there was a way to easily perform repairs without having to remove complete valves from the line. Removal and reinstallation cost of flanged valves is a very costly part of the repair process.
The primary purpose of the valve of the present invention is to permit field disassembly and assembly without having to cut, spring or unbolt a rotary valve from the line to which it is connected. The further advantage is that the environmental leakage and fire hazard that occurs at valve-to-pipe joints can be eliminated by making a valve integral with the pipe, mainly by way of welding. Rotary valves are best assembled by stacking the internal parts along the axis of flow. To achieve this optimum assembly once the valve is installed requires the removal of the valve or the use of a flowpath that is turned enough away from the direction of flow at the valve inlet so as to dispose a flow axis to an opening which will facilitate flow axis parts installation. This turning of a rotary valve's flowpath (at the expense of flow capacity) to simplify field repair is the essence of the AERo valve.
As explained previously, flow turns within an AERo valve can take place in the body inlet and outlet flow chambers and in a removable component called the DVC (downstream valve component). Embodiments are shown herein in which the flow is turned within the valve member rather than the DVC. Embodiments described hereinafter as "flow turning embodiments" comprise a combination of the DVC and valve member functions into a unitary member.
In addition, an embodiment called the "compression plate retainer", will also be described.